The overall goal of this research proposal is to examine the mechanisms by which environmental toxicants adverse;y affect reproductive neuroendocrine development, using the rat as a model. There are four specific aims: The goal of specific aim I is to establish am experimental model for evaluating development. Specific aim II will test the hypothesis that the GnRH neurosecretory system plays a critical role in environmental toxicant induced stimulation or delay of reproductive development; characterize the mechanisms and compare the effects of the different toxicants. Specific aim III will test the hypothesis that exposure to environmental toxicants affects the development of neurotransmitter/growth factor system inputs to GnRH neurons, hypothalamine GT1-7 neuronal cell line, which synthesizes and secretes GnRH, methoxychlor, Aroclor 1221, Aroclor 1254, lead and chlorpyrifos affect the GnRH neurosecretory system.